Change links for Babel to new docs location.

[tswast]

The header at https://babel.edgewall.org/ says

The Babel project has moved!
After this project has sadly been stalled for a long time, Armin Ronacher (@mitsuhiko) of Flask fame has kindly volunteered to get the project back up to speed. For a variety of reasons this means Babel is leaving the Edgewall.org umbrella.

The new home of the project is at babel.pocoo.org, the code is now hosted on Github at github.com/mitsuhiko/babel. In the coming days, we will make the Babel Trac environment on edgewall.org readonly

[jeffwidman]

LGTM